A tire is designed to withstand the weight of an automobile, reduce impact force exerted by the road, and transfer driving force or braking force of an automobile to the ground. In general, a tire is a complex of fiber/steel/rubber, and has a structure as shown in FIG. 1.
Tread (1) is a part contacting the road. It should afford frictional forces required for driving/braking, have superior wear and heat resistance, and withstand external impact force.
Body ply, or carcass (6) is a cord layer inside the tire. It should be able to support the weight of an automobile, withstand impact force, and have high resistance to fatigue caused by bending and stretching during automobile operation.
Belt (5), mainly made up of a steel wire, is located between the body plies, adapted to reduce external impact force and maintains a wide contact area of the tread for vehicle running stability.
Side wall (3) is a rubber layer between a part below a shoulder (2) and bead (9). It protects the body ply (6).
Inner liner (7), in replacement of a tube, is located inside the tire, and allows a pneumatic tire by preventing air leakage.
Bead (9), a square or hexagonal wire bundle formed of rubber-coated steel wires, serves to position and fix the tire in a rim.
Cap ply (4) is a special cord located on a radial tire belt, and minimizes the belt movement during operation of an automobile.
Apex (8) is a triangular rubber filler designed to minimize the bead displacements, protect the beads by alleviating external impact force, and prevent air inflow during the tire construction.
Recently, a tubeless tire injected with a high air pressure of 30 to 40 psi has been commonly used. In such tire, an inner liner having high gas barrier properties is positioned on the inner layer of the carcass to prevent air leakage during automobile operation.
Moreover, as a main ingredient, a tire inner liner including a rubber such as butyl rubber or halobutyl rubber and the like having relatively low air permeability has been previously used. In order to achieve sufficient gas barrier properties for such inner liner, however, an increase in the amount of the rubber content or in the thickness of the inner liner thickness has been required. As a result, the total weight of the tire was increased, thereby decreasing fuel efficiency. In addition, during tire vulcanization or vehicle operation, air pockets were generated between the inner rubber of the carcass layer and the inner liner, or the deformation or deviation of the shapes or properties of the inner liner have been observed.
Various methods have been suggested to minimize the thickness and weight of the inner liner to increase fuel efficiency, and maintain the shape or properties of the inner liner during tire vulcanization or vehicle operation.
These methods, however, have limitations in providing excellent air permeability and formability of a tire while sufficiently decreasing the thickness and weight of the inner liner. Further, the use of an additional tie gum rubber for a strong bonding to a carcass layer inside the tire increases the weight of a tire and degrades fuel efficiency. The inner liner manufactured according to the methods has not shown sufficient fatigue resistance, generating cracks, for instance, from repeated deformations during the manufacturing process or operation.
Accordingly, there is a demand for the development of a film for a tire inner liner to provide a lightweight tire having a thinner thickness that may withstand repeated deformations with excellent properties including gas barrier properties, formability, and the like.